Use of a chemically active reticle carrier for photomask etching

ABSTRACT

A method and apparatus for improving etch uniformity in reticle etching by eliminating local effects at the edge of the reticle is disclosed. The present invention relates to a reticle frame which surrounds the reticle. The reticle frames are patterned with a pattern profile similar to that of the reticle to prevent edge uniformities of the reticle by allowing uniform plasma etching of the entire reticle surface. The reticle frames may also be used to move the reticle in and out of etch chambers without damaging them.

FIELD OF THE INVENTION

The present invention relates to the field of photolithography used infabricating semiconductor devices and, more particularly to a method andapparatus for improving etch uniformity in reticle etching byeliminating local etching effects at the edge of the reticle.

DESCRIPTION OF THE RELATED ART

In the manufacture of semiconductor wafers, photolithography is used topattern various layers on a wafer. A layer of resist is deposited on thewafer and exposed using an exposure tool and a template such as a maskor reticle. During the exposure process a form of radiant energy, suchas ultraviolet light, is directed through the reticle to selectivelyexpose the resist in a desired pattern. The resist is then developed toremove either the exposed portions, for a positive resist, or theunexposed portions, for a negative resist, thereby forming a resist maskon the wafer. The resist mask can then be used to protect underlyingareas of the wafer during subsequent fabrication processes, such asdeposition, etching, or ion implantation processes.

An integral component of the photolithographic process is the reticle.The reticle includes the pattern corresponding to features (e.g.,transistors or polygates) at a layer of the integrated circuit (IC)design. The reticle may be a transparent glass plate coated with apatterned light blocking material such as, for example, chromium. Thistype of reticle is typically referred to as a binary mask since light iscompletely blocked by the light blocking material and fully transmittedthrough the transparent glass portions.

Another type of reticle is the attenuated phase shift mask (PSM).Attenuated PSMs utilize partially transmissive regions instead of thelight blocking regions used in binary masks. The partially transmissiveregions typically pass (i.e., do not block) about three to eight percentof the light they receive. Moreover, the partially transmissive regionsare designed so that the light that they do pass is shifted by 180degrees in comparison to the light passing through the transparent(e.g., transmissive) regions.

During the fabrication of reticles, the reticle is often affected byedge effects in the etching chamber. Reference is made to FIGS. 1-3.FIG. 1 shows a plasma etching system 10 including a radio frequency(“RF”) source power supply 11, a coil 12, a chamber 13, a dielectricplate 9, a multi-frequency bias power supply 15, and a decouplingcapacitor 16. The chamber 13 is connected to a ground potential 17.Reticle 18 is mounted onto electrode 14 which applies a bias voltage orbottom power. Electrode 14 may be an electrostatic-chuck or susceptorfor holding the reticle 18 during the etching process. Modulated-biasplasma 19 is generated in chamber 13 from source material 20. Sourcematerial 20 may be provided to chamber 13 via one or more feed tubes 52.Reticle has a chrome layer 21 formed thereon and a patterned photoresistlayer 22 formed over chrome layer 21. Reticle 18 is reacted with plasma19 to etch a portion of a surface of chrome layer 21 according to thepatterned photoresist 22 to impart the pattern onto the reticle 18. Ascan be seen from FIGS. 1-3, the reticle 18 is positioned directly overelectrode 14. As the plasma bombards the reticle, it etches the reticleon an upper surface as well as at the edges of the reticle 18. FIG. 2shows a top view of the etched reticle and FIG. 3 shows a cross sectionof the reticle as shown in FIG. 2. The reticle suffers from edge effectsin the etching of the reticle. These edge effects are caused by theexistence of the edge of the reticle and the nonuniformity in thereticle formed due to nonuniformity of chemical loading and electricalpower at the edge of the reticle. The edge effects may be manifest as adifferent print quality at the edge of the reticle. Thus, if anintegrated circuit pattern extends to the edge of the reticle it will beadversely affected by these edge effects.

There is a need to eliminate edge effects in the reticle to prevent edgeanomalies from being transferred onto an integrated circuit or onto amask used in fabrication of an integrated circuit. This is especiallytrue as feature sizes continue to dramatically decrease, and as thenumber of features within the IC design continues to increase, itrequires reticles which can use a greater portion of the surface fortransferring a pattern to an integrated circuit. Accordingly, there is aneed and desire for a method and apparatus for eliminating edge effectsfrom the high density etchers in the formation of reticles.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for improving etchuniformity in reticle etching by eliminating local effects at the edgeof the reticle. Specifically, the invention relates to a reticle carrierwhich surrounds the reticle and is subjected to a plasma etch along withthe reticle to reduce edge non-uniformities. The reticle carrier mayalso be used to move reticles in and out of etch chambers withoutdamaging or contaminating them. To help reduce edge non-uniformities,the reticle carriers are formed of materials similar to that of thereticle and are patterned with a pattern profile similar to that of thereticle.

Additional advantages of the present invention will be apparent from thedetailed description and drawings, which illustrate preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages and features of the invention willbecome more apparent from the detailed description of the preferredembodiments of the invention given below with reference to theaccompanying drawings in which:

FIG. 1 is a schematic view of a conventional plasma etching system.

FIG. 2 is a top view of a conventional reticle placed on a chuck.

FIG. 3 is a view taken along the line III—III of FIG. 2.

FIG. 4 is a top view of a reticle placed on the reticle carrieraccording to the present invention.

FIG. 5 is a view of the reticle carrier of the present invention takenalong the line V—V of FIG. 4.

FIG. 6A is a cross sectional view of the reticle and carrier accordingto a second embodiment of the present invention.

FIG. 6B is a cross sectional view of the reticle and carrier accordingto a third embodiment of the present invention.

FIG. 7 is a schematic view of a reticle plasma etching system using areticle carrier according to the present invention.

FIG. 8 shows a reticle undergoing an intermediate stage of processingaccording to the present invention.

FIG. 9 a reticle undergoing a processing according to the presentinvention at a point subsequent to that shown in FIG. 8.

FIG. 10 a reticle undergoing a processing according to the presentinvention at a point subsequent to that shown in FIG. 9.

FIG. 11 a reticle undergoing a processing according to the presentinvention at a point subsequent to that shown in FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized, and thatstructural, logical and electrical changes may be made without departingfrom the spirit and scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,as the scope of the present invention is defined by the appended claims.

Reference is now made to FIG. 4. This figure shows a top view of thereticle 118 and frame 123 surrounding reticle 118 according to thepresent invention. While the reticle 118 is depicted as square in shapeand the frame 123 is depicted as being circular in shape, it should beunderstood that these components could be any desired shape. Forexample, both the reticle 118 and the frame 123 may be rectangular inshape. The reticle 118 may be formed of any suitable material forexample, silica glass, fused quartz glass, borosilicate glass or anothermaterial transparent to various types of radiation commonly used insemiconductor lithographic operations. Preferably the reticle is formedof quartz. Further, the reticle may be any reticle including a lightblocking reticle, a phase shifting reticle, an attenuated phase shiftingreticle, a hard phase shift reticle or a multi-layered phase shiftingreticles.

Reticle 118 has formed thereon patterned light blocking or partiallylight transmissive regions 121 formed on the surface of the reticle 118depending upon whether the reticle is a binary reticle or a phaseshifting reticle. The light blocking regions 121 can be a homogeneousmetal layer, such as chrome, gold, or the like. Alternatively, the lightblocking regions 121 may be a composite material of different metals,such as chrome and gold, or chrome and another metal, or the like. Inyet another alternative, partially light transmissive regions 121 can beformed of any attenuating material employed in a phase shifting mask,such as, for example, molybdenum silicide.

The reticle 118 is placed on frame 123. Frame 123 is formed of amaterial similar to that of reticle 118 such that the reticle 118 andframe 123 have similar chemical and electrical properties in the plasmaetcher. Accordingly, it is preferable that the frame 123 be formed ofsilica glass, fused quartz glass, borosilicate glass or another materialtransparent to various types of radiation commonly used in semiconductorlithographic operations. Preferably the frame 123 is formed of quartz.

The frame 123 is also patterned with a light blocking or partially lighttransmissive region similar to that of reticle 118. Thus, frame 123 hasformed thereon patterned light blocking or partially light transmissiveregions 124 formed on the surface of the frame 123 depending uponwhether the reticle 118 is a binary reticle or a phase shifting reticle.The light blocking regions 124 can be a homogeneous metal layer, such aschrome, gold, or the like. Alternatively, the light blocking regions 124may be a composite material of different metals, such as chrome andgold, or chrome and another metal, or the like. In yet anotheralternative, partially light transmissive regions 124 can be formed ofan attenuating material employed in a phase shifting mask, such as, forexample, molybdenum silicide.

The light blocking or partially light transmissive region 124 formed onframe 123 may be formed during the formation of light blocking orpartially light transmissive region 121 on reticle 118, or at a timeprior to or subsequent to the patterning of the reticle 118. This isdiscussed in more detail below in reference to the method for formingthe reticle 118 with reference to FIGS. 8-9.

Reference is now made to FIG. 5. This figure is a cross sectional viewalong line V—V as shown in FIG. 4. As can be seen from the figure, thereticle 118 is supported at a bottom layer of reticle 118 by L-shapedsections of frame 123. While frame 123 is shown as having L-shapedsections near the bottom of the frame 123, it should be understood thatany suitable support may be used to support reticle 118 within frame123. For example, the frame may have angled support pieces or round nubsformed at the bottom of the frame to support reticle 118. In addition,frame is designed such that the upper surface of reticle 118 and frame123 are essentially coplanar.

An alternative embodiment of the present invention is shown withreference to FIGS. 6A and 6B. Reference is first made to FIG. 6A. Thisfigure shows a reticle 138 having a portion of the bottom of the reticle138 cut away in a square cross section so as to engage protrudingportions 135 of frame 133. Reference is now made to FIG. 6B wherereticle 148 having a portion of the bottom of the reticle 148 cut awayin a triangular cross section so as to engage complimentary triangularprotruding portions 145 of frame 143. As can be seen from FIGS. 6A and6B, the upper and lower surfaces of the reticles 138, 148 are coplanarwith the upper and lower surfaces of frames 133, 143. The presence ofportions of frame 123, 133, 143 directly adjacent to the edges ofreticle 118, 138, 148 provides a more uniform etching surface on bothsides of the reticle, which, in turn, allows even chemical loading andelectrical power across both the reticle 118, 138, 148 and frame 123,133, 143 using a conventional plasma etching apparatus similar to thatdepicted in FIG. 1.

Reference is made to FIG. 7 which shows a plasma etching system 110including a radio frequency (“RF”) source power supply 111, a coil 112,a chamber 113, a dielectric plate 109, a multi-frequency bias powersupply 115, and a decoupling capacitor 116. The chamber 113 is connectedto a ground potential 117. Reticle 118 is mounted on a frame 123 andthen mounted onto an electrode 114 which applies a bias voltage orbottom power. Electrode 114 is formed such that electrode 114 contactsboth frame 123 and reticle 118. The electrode 114 may have a raisedcolumn structure to efficiently contact both the frame 123 and electrode118 as illustrated in FIG. 7.

Modulated-bias plasma 119 is generated in chamber 113 from sourcematerial 120. Source material 120, such as, for example, HBr, O₂, Ar,Cl, fluorocarbon containing gases and the like, may be provided tochamber 113 via one or more feed tubes 152. Reticle 118 has a lightblocking or partially light transmissive region, such as a chrome layer,121 formed thereon and a patterned photoresist layer 125 formed overchrome layer 121. Frame 123 has a light blocking or partially lighttransmissive region, such as a chrome layer, 124 formed thereon and apatterned photoresist layer 122 formed over chrome layer 124 in themanner described above. Reticle 118 and patterned frame 123 are reactedwith plasma 119 to etch a portion of a surface of chrome layer 121, 124according to the patterned photoresist 125, 122 to impart the patternonto the reticle 118 and frame 123. Reticle 118 and frame 123 are thenremoved from the chamber 113, reticle 118 is removed from frame 123 andthe remaining photoresist layers 125 are removed from the reticle 118.

As can be seen from FIG. 7, the reticle 118 is positioned within frame123 and both frame 123 and reticle 118 are in direct contact withelectrode 114. As the plasma bombards and etches the reticle 118, italso bombards and etches the frame 123, thus reducing the edge effect atthe upper surface of reticle 118 caused by nonuniformity in chemicalloading and electrical power at the edge of reticle 118. Thus, a greatersurface area of the reticle can be used to transfer a pattern onto anintegrated circuit. Additionally, by eliminating edge effects, thepresent invention allows the use of the perimeter of the surface of thereticle which are currently not patterned. The present inventiontherefore would provide an increase of greater than about 150 mm² ofreticle surface area to transfer patterns to an integrated circuitdevice.

The method for fabricating a reticle according to the present inventionwill now be described with reference to FIGS. 8-11. Reference is firstmade to FIG. 8. A light blocking or partially light transmissive layer121 is deposited over a reticle substrate 118 which may be formed ofsilica glass, fused quartz glass, borosilicate glass or another materialtransparent to various types of radiation commonly used in semiconductorlithographic operations, by any conventional method. Light blocking orpartially light transmissive layer 121 is then deposited which may beany suitable material such as a homogeneous metal layer, such as chrome,gold, or the like or a composite material of different metals, such aschrome and gold, or chrome and another metal, or the like. Lightblocking or partially light transmissive layer 121 may also be anattenuating material employed in a phase shifting mask such as amolybdenum silicide. A pattern transfer layer 125 is then deposited overlight blocking or partially light transmissive layer 121. Patterntransfer layer 125 may be any material used to transfer a pattern to asubsequent layer and will depend upon the radiation characteristics ofthe equipment used to form the lithographic reticle 118. For example,where an electron beam direct write system is used, pattern transferlayer 125 will be formed of an electron beam sensitive photoresist.Alternatively, where an optical system is used to generate radiation ofa particular wavelength, pattern transfer layer 125 will be aconventional photoresist material sensitive to the particularwavelength. It should be understood that those skilled in the art willrecognize that many different combinations of materials can be used toform the layers shown in FIG. 8.

Reference is made to FIG. 9. After preparing reticle substrate 118 withlight blocking or partially light transmissive layer 121 and patterntransfer layer 125, pattern transfer layer 125 is exposed to radiationby a scanning electron beam or laser. Radiation emerging from aradiation source is imaged onto pattern transfer layer 125. The imagingprocess results in the transfer of a pattern present in a reticlegenerating data base to pattern transfer layer 125.

The pattern transfer layer 125 is written with an electron beam directwrite system and the pattern transfer layer is developed to arrive atthe structure illustrated in FIG. 9. The present invention contemplatesthe use of many different types of pattern transfer layer 123 dependingupon the particular lithographic system to be used in the fabrication ofsemiconductor devices, this includes deep-ultraviolet (deep UV), x-ray,and standard i-line and g-line lithographic systems. While the transferof pattern will typically use an electron beam direct write system, itis also possible to perform pattern transfer using an optical imagingprocess using radiation having a wavelength ranging from the deep-UV toabout 200 nanometers to optical wavelengths up to about 440 nanometers.

The lithographic pattern may includes a large number of patterned metalfeatures overlying reticle substrate 118. The exact arrangement of thelithographic pattern will depend upon the particular masking level forwhich lithographic reticle 118 is to be used. For example, wherelithographic reticle 118 is to be used to form interconnect traces in asemiconductor device, the lithographic pattern will include a series oflead traces having the necessary geometric arrangement to form metalinterconnects in a semiconductor device. In other applications, reticle118 can be used to form, for example, gate electrodes in a semiconductordevice, or via openings in an interlevel dielectric layer, and the like.

It should be understood that those skilled in the art will recognize thereticles can be of two general types, either brightfield or darkfield.In a brightfield reticle patterned features to be transferred are opaquefeatures on a clear background. The process of the invention is intendedto function with either type of reticle. In the case of a darkfieldreticle, the lithographic pattern will appear as openings in a sheet ofopaque material overlying reticle substrate 118.

Reference is now made to FIG. 10. Reticle 118 having a light blocking orpartially light transmissive region 121 overlying reticle substrate 118and a pattern transfer layer 125 overlying light blocking or partiallylight transmissive region 121 is placed on reticle frame 123. Reticleframe 123 is independently deposited with a light blocking or partiallylight transmissive layer 124 and patterned with a pattern transfer layer122. Because the frame 123 will ultimately be discarded, it is notessential that the frame be patterned with the precision of the electronbeam writing system as used for reticle 118. In fact, the frame 123 maybe patterned with crude lithography of about 2 to 3 times the designgeometry rule of reticle 118. While the frame 123 should be patternedwith approximately the same pattern density as reticle 118, frame 123does not need to be patterned with the same precision as reticle 118.This allows efficient use of the writing system. While the presentinvention has been described by patterning the frame 123 and reticle 118separately, it should be understood that reticle 118 and frame 123 mayalso be patterned in the same step. The reticle 118 and frame 123 arethen placed onto an electrode 114 in a high-density plasma etcher, asdepicted in FIG. 10.

Reference is now made to FIG. 11. After preparing reticle substrate 118with light blocking or partially light transmissive region 121 andpattern transfer layer 125 and preparing frame 123 with light blockingor partially light transmissive region 124 and pattern transfer layer122, the light blocking or partially light transmissive regions 121, 124are removed from the reticle 118 and frame 123 in a high-density plasmaetcher. Since the reticle 118 and frame 123 are both formed of materialsthat are electrically and chemically similar and have similar patterndensity, edge effects in the plasma etcher are reduced or eliminated.Thus, the reticle can be formed such that a greater surface of thereticle may be patterned.

While the invention has been described in detail in connection with thepreferred embodiments known at the time, it should be readily understoodthat the invention is not limited to such disclosed embodiments. Rather,the invention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Accordingly, the invention is not to be seen as limited bythe foregoing description, but is only limited by the scope of theappended claims.

What is claimed is:
 1. A method for etching a reticle comprising:providing a reticle having at least a first light blocking or partiallylight transmnissive layer thereon and at least a first pattern transferlayer on said first light blocking or partially light transmissivelayer; providing a frame having an opening for receiving said reticle,said frame having at least a second light blocking or partially lighttransmissive layer thereon and at least a second pattern transfer layeron said second light blocking or partially light transmissive layer,wherein said second light blocking or partially light transmissive layerhas physical and chemical properties which will increase uniformity ofthe etching of said reticle when said frame containing said reticle isexposed to a plasma; placing said reticle in said frame; and etchingsaid reticle and frame with a plasma.
 2. The method according to claim1, wherein said first light blocking or partially light transmissivelayer is a light blocking layer.
 3. The method according to claim 1,wherein said first light blocking or partially light transmissive layeris a partially light transmissive layer.
 4. The method according toclaim 2, wherein said second light blocking or partially lighttransmissive layer is a light blocking layer.
 5. The method according toclaim 3, wherein said second light blocking or partially lighttransmissive layer is a partially light transmissive layer.
 6. Themethod according to claim 1, wherein said first light blocking orpartially light transmissive layer comprises chrome.
 7. The methodaccording to claim 6, wherein said second light blocking or partiallylight transmissive layer comprises chrome.
 8. The method according toclaim 1, wherein said first light blocking or partially lighttransmissive layer comprises molybdenum silicide.
 9. The methodaccording to claim 8, wherein said second light blocking or partiallylight transmissive layer comprises molybdenum silicide.
 10. The methodaccording to claim 1, wherein said first pattern transfer layer isphotoresist.
 11. The method according to claim 1, wherein said reticleis formed of a material selected from the group consisting of quartz,silica glass and borosilicate glass.
 12. The method according to claim11, wherein said frame is formed of a material selected from the groupconsisting of quartz, silica glass and borosilicate glass.
 13. Themethod according to claim 1, wherein said first light blocking orpartially light transmissive layer is selected from the group consistingof chrome, gold and molybdenum silicide.
 14. The method according toclaim 1, wherein said second light blocking or partially lighttransmissive layer is selected from the group consisting of chrome, goldand molybdenum silicide.
 15. The method according to claim 1, furthercomprising forming said first light blocking or partially lighttransmissive layer and said first pattern transfer layer on said firstlight blocking or partially light transmissive layer of said reticle ata time different from that of forming said second light blocking orpartially light transmissive layer and said second pattern transferlayer on said second light blocking or partially light transmissivelayer of said frame.
 16. The method according to claim 1, furthercomprising forming said first light blocking or partially lighttransmissive layer and said first pattern transfer layer on said firstlight blocking or partially light transmissive layer of said reticle atthe same time as forming said second light blocking or partially lighttransmissive layer and said second pattern transfer layer on said secondlight blocking or partially light transmissive layer of said frame. 17.A method for forming a reticle comprising: providing a reticlesubstrate; forming at least a first light blocking or partially lighttransmissive layer thereon; forming at least a first pattern transferlayer on said first light blocking or partially light transmissivelayer; patterning said pattern transfer layer with a predeterminedpattern; providing a frame having an opening to support said reticle;forming at least a second light blocking or partially light transmissivelayer on said frame; forming at least a second pattern transfer layer onsaid second light blocking or partially light transmissive layer,wherein said second light blocking or partially light transmissive layerhas physical and chemical properties which will increase uniformity ofthe etching of said reticle when said frame containing said reticle isexposed to a plasma; patterning said second pattern transfer layer witha predetermined pattern; placing said reticle in said frame; and etchingsaid reticle and said frame with a plasma.
 18. The method according toclaim 17, wherein forming said first light blocking or partially lighttransmissive layer includes forming a light blocking layer.
 19. Themethod according to claim 17, wherein forming said first light blockingor partially light transmissive layer includes forming a partially lighttransmissive layer.
 20. The method according to claim 18, whereinforming said second light blocking or partially light transmissive layerincludes forming a light blocking layer.
 21. The method according toclaim 17, wherein forming said second light blocking or partially lighttransmissive layer includes forming a partially light transmissivelayer.
 22. The method according to claim 17, wherein forming said firstlight blocking or partially light transmissive layer includes forming achrome layer.
 23. The method according to claim 22, wherein forming saidsecond light blocking or partially light transmissive layer includesforming a chrome layer.
 24. The method according to claim 17, whereinforming said first light blocking or partially light transmissive layercomprises forming a molybdenum silicide layer.
 25. The method accordingto claim 24, wherein forming said second light blocking or partiallylight transmissive layer comprises forming a molybdenum silicide layer.26. The method according to claim 17, wherein said first patterntransfer layer is photoresist.
 27. The method according to claim 17,wherein said first pattern transfer layer is patterned by an electronbeam.
 28. The method according to claim 17, wherein an upper surface ofsaid reticle and an upper surface of said frame are coplanar.
 29. Themethod according to claim 17, wherein said reticle is formed of amaterial selected from the group consisting of quartz, silica glass andborosilicate glass.
 30. The method according to claim 29, wherein saidframe is formed of a material selected from the group consisting ofquartz, silica glass and borosilicate glass.
 31. The method according toclaim 17, wherein said first light blocking or partially lighttransmissive layer is selected from the group consisting of chrome, goldand molybdenum silicide.
 32. The method according to claim 31, whereinsaid second light blocking or partially light transmissive layer isselected from the group consisting of chrome, gold and molybdenumsilicide.
 33. The method according to claim 30, wherein said reticle andsaid frame are formed of the same material.
 34. The method according toclaim 32, wherein said first and second light blocking or partiallylight transmissive layer are formed of the same material.
 35. A methodfor etching a reticle comprising: placing a reticle having a patternedlayer thereon to be etched in a frame, whereby said edges of saidreticle abut inside side edges of said frame and a top layer of saidreticle is coplanar with a top layer of said frame, said frame having aproperty of reducing side edge effects from forming in said reticle whensaid reticle is placed in said frame and said reticle and said frame areexposed to a plasma etching environment; and etching said reticle whilein said frame in a plasma etching environment.
 36. The method accordingto claim 35, wherein said reticle is formed of a material selected fromthe group consisting of quartz, silica glass and borosilicate glass. 37.The method according to claim 35, wherein said frame is formed of amaterial selected from the group consisting of quartz, silica glass andborosilicate glass.
 38. The method according to claim 35, wherein saidreticle is patterned with a layer is selected from the group consistingof chrome, gold and molybdenum silicide.
 39. The method according toclaim 35, wherein said frame is patterned with a layer is selected fromthe group consisting of chrome, gold and molybdenum silicide.
 40. Themethod according to claim 35, wherein said reticle and said frame areformed of the same material.
 41. The method according to claim 40,wherein said reticle and said frame are formed of quartz.
 42. The methodaccording to claim 35, wherein said reticle and frame are patterned withthe same material.
 43. The method according to claim 42, wherein saidmaterial is chrome.